This invention concerns a system to install the rolling rings on a rolling roll.
To be more exact, the system according to the invention is used to install the rolling rings, which generally but not only are made of cast iron, on the relative supporting half-shafts.
The invention is applied in particular but not only to rolling mill stands for single-channel roughing rolling with box passes or diamond passes.
In rolling mill stands of the state of the art and, in particular, in universal rolling mill stands a procedure of keying the rolling rings to a pair of half-shafts, which are coupled together and face each other substantially at the centre line of the relative rolling ring, has been disclosed.
These half-shafts are generally kept under tension by pre-loaded tie rods inserted coaxially into the half-shafts.
These pre-loaded tie rods ensure a union between the half-shafts in each working step and also transmission of the torque.
The half-shafts include lateral flanges which cooperate by contact with the lateral surfaces of the rolling rings.
The torque is transmitted by friction through these flanges to the rolling rings.
The systems disclosed in the state of the art for the coupling of the half-shafts involve some drawbacks, especially as regards the deflections under load which take place in general in all the rolling steps and which may be especially damaging in the event of severe working conditions.
According to the installation system of the state of the art the half-shafts are kept reciprocally under tension by pre-loaded tie rods, but no type of reciprocal support is created between one half-shaft and the other half-shaft.
In particular, at the centre line of the rolling rings, where the transverse deflection under load takes on the highest values, there is a zone of coupling of the two half-shafts which coincides with the zone of less resistance to stresses applied in a direction perpendicular to the axis of the half-shafts themselves.
Another drawback often encountered in installation systems of this type concerns the rapid wear to which the parts of reciprocal cooperation of the half-shafts are subjected, namely the relative inner ends.
This rapid wear involves frequent corrective work on important parts of the half-shafts, long times for dismantling the elements to be maintained, the use of a labour force and still other problems.
Moreover, in view of the considerable cost and effort required, this corrective work often tends to be postponed, thereby entailing working conditions which are not always the best.